The present invention relates to information printers of the dot-matrix type and, more particularly, to novel stacked blade arrangements for the printhead thereof.
Mechanisms capable of printing characters, symbols and the like along a line upon underlying media, such as a paper document and the like, have been generally classifiable into one of two types: whole-character and dot-matrix.
One known embodiment of a whole-character printer utilizes a drum, having a raised-type portion for forming each indicia printable, which rotates adjacent one face of the printing media; a relatively wide hammer member is electrically actuated to impact the remaining surface of the printing media and press the media and an inked ribbon against the rotating indicia drum at the exact instant that the desired character is passing thereunder. As is obvious, the synchronization problems associated with a whole-character printer are awesome, particularly when individual drums are stacked in side-by-side manner along a print line typically containing up to 132 character positions, with all 132 individual striking hammers requiring separate synchronization with only that one of the continuously rotating drums associated therewith.
The dot matrix printer attempts to overcome this problem by incrementally forming each sequential character by selective impingement of one or more print elements arranged along a vertical line. In a typical application, seven print wires have their tips arranged along the vertical line and each print wire is energized by an associated solenoid means to print a single dot on the vertical line. As the printhead moves to five equally spaced, sequential column positions (with a sixth column being left empty to provide a space between characters), the print wire tips impinge upon the printing media to form the desired character pattern.
This approach has the general limitations of: somewhat poor character legibility; inability of the printer to form upper and lower case characters due to low density patterns; and excessive frictional wear both between the print wires and their guides and between the print wires and the inked ribbon. Additionally, each print wire must be driven by a separate solenoid, having its own individual magnetic structure with most of the length of an iron flux path therein being excited by the solenoid coil such that an armature, attached to the printing wire, is caused to move to close the flux path. This complex and costly construction for a dot-matrix printhead is undesirable, as is the consequent saturation of the magnetic structure and high printing wire reciprocating speeds. Apparatus is desired which overcomes many, if not all, of the wire-type dot-matrix printer problems, while enabling a relatively simple and cost-effective construction even with high matrix density print capability.